Carbonate-hosted base metal deposits: lead isotope data bearing on their genesis and exploration.

Four Australian carbonate-hosted Pb-Zn deposits have different Pb isotope patterns. The distinctive Pb isotope compositions persist through weathering, an observation of use in gossan evaluations. Comparison of the Australian data on a global basis identifies two main groups of isotope patterns: 1) homogeneous Pb isotope compositions, with a radiogenic subdivision and 2) heterogeneous compositions that are generally radiogenic. Lateral secretion is the favoured origin for carbonate-hosted deposits with: 1) homogeneity dependent on proximity of the ores to deep sedimentary basins (a form of mixing vat) and 2) radiogenic Pb as a function of the age difference between the host carbonate and the crystalline basement.-G.J.N.